Lappa IV was the fourth planet in its star system. It was affiliated with the Ferengi.

Zan Periculi, a species of flower, was indigenous to this planet. (TNG: "Ménage à Troi")

According to Star Trek: Star Charts ("United Federation of Planets I") and Stellar Cartography: The Starfleet Reference Library ("Federation Historical Highlights, 2161-2385"), the Lappa system was located in the Alpha Quadrant. The system's primary was a K-class star.
"Choose Your Pain" establishes that Zan Periculi was already known to the Federation in 2256, which might mean the planet was known also.